The present invention relates to methods and apparatus for joining together a web from a new roll of material to a web from an expiring roll that is being fed to a printing press or other continuous web processing operation. The material may be paper, film, foil, laminate, etc.
A common method that has been used to join or splice such webs in the past is the so-called lap joint. The leading end of the new web is treated with a suitable adhesive, and at the proper time, is manually lapped over the trailing end of the expiring roll. U.S. Pat. No. 4,519,858 describes an apparatus and method for making such lap joints.
A lap joint or splice produces, however, an undesirable double thickness of material at the joint or splice. Further, certain materials, such as two-ply pressure-sensitive label stock, cannot usually be spliced in a lap joint because of restrictive operations downstream of the joint.
Another commonly used method to join new and expiring webs is the so-called butt splice. In such butt splice or joint, the leading end of the new roll is "butted-up" closely to, but is not overlapped with the trailing end of the expiring roll. A relatively thin, single-sided pieces of adhesive tape is used to join the "butted" ends together.
A butt splice or joint may be used to joint two ply material, such as pressure-sensitive label stock. With such material, pieces of adhesive tape must be used on both sides of the material so that when the plies are pulled apart, the web will remain joined.
A good quality butt joint or splice has less than a one/one thirty-second inch gap between the butted ends of the webs from the new and expiring rolls, with the ends being aligned closely. When adhesive tape is used on both sides of the web, the adhesive on one tape should not touch the adhesive on the other tape.
Traditionally, hand operations have had to be used to achieve a good quality butt splice or joint, particularly when splicing two-ply materials. The accuracy required necessitates the stopping of the web from the expiring roll for a sufficient time to make a hand splice. Such stoppage results in a significant loss of production time as each roll expires.